Generally, a hybrid control unit (HCU) of a hybrid vehicle controls the operation of an engine, a generator and a motor of the hybrid vehicle and causes the hybrid vehicle to be driven in an optimal state. In other words, the HCU controls the hybrid vehicle such that the vehicle can be driven in an appropriate driving mode, selected between a HEV mode, an EV mode and a MAX torque mode according to both a required torque and the state of charge (SOC) of a battery. As well known to those skilled in the art, the HEV mode is a driving mode in which the HCU drives the hybrid vehicle using both the engine and the motor. In the EV mode, the hybrid vehicle is driven using only the motor and power of the battery. In the MAX torque mode, the hybrid vehicle is driven both by the engine and by the motor such that, if the required torque in the MAX torque mode is not provided by the HEV mode, the engine is operated in the maximum torque mode and the remaining part of the required torque is provided by the motor. Furthermore, the hybrid vehicle may be driven in a regeneration mode, wherein the battery is charged with electricity while braking force is applied to the vehicle.
In the prior art, the HCU selects an appropriate driving mode for the hybrid vehicle using a control algorithm stored therein. However, an error may occur while the HCU selects an appropriate driving mode for the hybrid vehicle. Furthermore, the conventional HCU does not have any means for detecting the occurrence of error or of informing a driver of the vehicle of the error, so that the conventional HCU may fail to maintain an optimal driving state of the hybrid vehicle.
Thus, the inventor of the present invention has actively studied monitoring logic that can be used by the HCU to determine which mode is consistent with the present driving mode of a hybrid vehicle.